【JavaWeb】JDBC工具类实现登录功能

我就是我 2023-02-27 12:23 41阅读 0赞

我们使用JDBC实现数据库的增删改查，代码基本差不多，有很多重复，所以我们可以把这些重复的代码写成一个工具类，使用的时候直接调用就可以了。下面以实现登录功能的案例来介绍。

**创建数据库，插入数据**

use student;
    create table user(
    	id int primary key auto_increment,
        username varchar(32),
        password varchar(32)
    );
    
    insert into user values(null,'zhangsan','123');
    insert into user values(null,'lisi','234');

**jdbc.properties**

url=jdbc:mysql://localhost:3306/student
    username=root
    password=root
    driver=com.mysql.jdbc.Driver

**JDBC工具类**

package cn.itcast.util;
    
    import java.io.FileReader;
    import java.io.IOException;
    import java.net.URL;
    import java.sql.*;
    import java.util.Properties;
    
    /* JDBC工具类 */
    public class JDBCUtils { 
        private static String url;
        private static String username;
        private static String password;
        private static String driver;
        /** * 文件的读取，著需要读取一次即可拿到这些值，使用静态代码块 */
        static { 
    
            try { 
                //1、读取资源文件，获取值
                Properties properties = new Properties();
    
                //获取src路径下的文件的方式 ---> ClassLoader类加载器
                ClassLoader classLoader = JDBCUtils.class.getClassLoader();
                URL resource = classLoader.getResource("jdbc.properties");
                String path = resource.getPath();
    
                //2、加载文件
                properties.load(new FileReader(path));
                //3、获取数据，赋值
                url = properties.getProperty("url");
                username = properties.getProperty("username");
                password = properties.getProperty("password");
                driver = properties.getProperty("driver");
                //4、注册驱动
                Class.forName(driver);
            } catch (IOException e) { 
                e.printStackTrace();
            } catch (ClassNotFoundException e) { 
                e.printStackTrace();
            }
        }
    
    
        /** * 获取连接 * @return 连接对象 */
        public static Connection getConnection() throws SQLException { 
            return DriverManager.getConnection(url,username,password);
        }
    
        /** * 释放资源 * @param statement * @param connection */
        public static void close(Statement statement,Connection connection) { 
            if (statement != null) { 
                try { 
                    statement.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
            if (connection != null) { 
                try { 
                    connection.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
        }
    
        /** * 释放资源 * @param resultSet * @param statement * @param connection */
        public static void close(ResultSet resultSet,Statement statement, Connection connection) { 
            if (resultSet != null) { 
                try { 
                    resultSet.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
            if (statement != null) { 
                try { 
                    statement.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
            if (connection != null) { 
                try { 
                    connection.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
        }
    }

**实现登录功能**

package cn.itcast.jdbc;
    
    import cn.itcast.util.JDBCUtils;
    
    import java.sql.*;
    import java.util.Scanner;
    
    /** * 1、通过键盘录入用户名和密码 * 2、判断用户是否登录成功 */
    public class JDBCLogin { 
    
        public static void main(String[] args) { 
            //1、键盘录入，接收用户和密码
            Scanner sc = new Scanner(System.in);
            System.out.println("请输入用户名：");
            String username = sc.nextLine();
            System.out.println("请输入密码：");
            String password = sc.nextLine();
            //2、调用方法
            boolean flag = new JDBCLogin().login(username,password);
            //3、判断
            if (flag) { 
                System.out.println("登录成功");
            } else { 
                System.out.println("用户名或密码错误！");
            }
        }
    
    
        /** * 登录方法 */
    
        public boolean login(String username,String password) { 
            if (username == null || password == null) { 
                return false;
            }
            //连接数据库判断是否登陆成功
    
    
            Connection connection = null;
            PreparedStatement preparedStatement = null;
            ResultSet resultSet = null;
            try { 
                //1、获取链接
                connection = JDBCUtils.getConnection();
                //2、定义sql
                String sql = "select * from user where username = ? and password = ?";
                //3、获取执行sql的对象
                //为了防止sql注入，实现事务安全，效率更高，必须要用PreparedStatement
                preparedStatement = connection.prepareStatement(sql);
                //给?赋值
                preparedStatement.setString(1,username);
                preparedStatement.setString(2,password);
                //4、执行查询，不需要传递sql
                resultSet = preparedStatement.executeQuery();
                //5、判断：如果是下一行，则返回true
                return resultSet.next();
            } catch (SQLException e) { 
                e.printStackTrace();
            } finally { 
                JDBCUtils.close(resultSet,preparedStatement,connection);
            }
            return false;
        }
    }

**运行结果：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 1]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 2]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70]: /images/20230209/85875fbcde4d4159ac69ea22e4e85fd7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 1]: /images/20230209/d2b3a872422548148bc8388902f66b06.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 2]: /images/20230209/0344d80a16c84a2b9b395c178c939c5f.png